Add the SQLITE_DEFAULT_SYNCHRONOUS and SQLITE_DEFAULT_WAL_SYNCHRONOUS
compile-time options. Automatically switch to the WAL_SYNCHRONOUS setting
when first opening a WAL-mode database if the synchronous setting has not
been previously set by the application.
check-in: 5a847a67 user: drh tags: trunk

If SQLITE_DEFAULT_WAL_SYNCHRONOUS is not the same value as
SQLITE_DEFAULT_SYNCHRONOUS and the application has not run
"PRAGMA synchronous", then set synchronous to the
SQLITE_DEFAULT_WAL_SYNCHRONOUS setting when entering WAL mode for
the first time.
check-in: 5791407b user: drh tags: default-synchronous